[pianotech] Un-Grand revisited

[Ron Nossaman]

On 12/13/2011 12:23 PM, Delwin D Fandrich wrote:
> If memory serves--and it may not--I think Robertson's square-drive screws
> was in use before the Phillips-type screw came along. I seem to recall
> reading somewhere that Henry used square-drive screws in his Model T. The
> Phillips screw wasn't invented until 1930 something. With the metallurgy of
> the day the Phillips-type screw could take more torque.

I've read that the Phillips was designed to cam out before it reached 
damaging torque levels, like the hex drive or Robertson. Kimball refined 
this to an art form by spinning bits in Phillips head screws until a 
smooth conical crater formed, eliminating all hope of removing the 
screws at some later date. Other manufacturers tried, but never quite 
reached Kimball's level of expertise at screw head stripping.


> Square-drive fasteners are great for assembly work as long as the drivers
> don't round over.

Or more likely, break. That was also the idea behind hex drive and the 
spline type that (I think) Aeolean used in their vertical backs.


>Even though the Phillips configuration took over in the
> U.S. there have always been a few holdouts who continued using square-drive
> screws. I guess Grand was one of them. Somebody back then told me Grand used
> Robertson's screws from the start. At least that was where I first saw
> them--I had to track down a driver with a square blade to fix one. In the
> 1960s in San Bernardino, CA that wasn't easy.

That sounds likely.
Ron N